State Route 233 (SR 233) is a state highway in rural Elko County, Nevada, USA. The highway follows the routes of the First Transcontinental Railroad and California Trail from Interstate 80 (I-80) to the Utah state line. The highway was formerly numbered State Route 30.

Interstate 80 follows the route of the First Transcontinental Railroad and the California Trail throughout most of Nevada, but departs these corridors east of Wells. These historical routes went around the north end of the Pequop Mountains, towards the north shore of the Great Salt Lake. Modern I-80 directly crosses these mountains in route to the south shore of the lake. State Route 233 exits Interstate 80 at exit 378 in Oasis, on the other side of the Pequops from Wells. Route 233 proceeds on a northeast course to rejoin the route of the railroad and trail. The highway passes through the community of Montello, Nevada in route to the Utah state line, where the highway continues as State Route 30. In Utah, the route also loosely follows the historical routes of the railroad and trail around the north side of the Great Salt Lake until connecting with Interstate 84.

This corridor loosely parallels the route of the California Trail, which was first used by emigrants during the California Gold Rush. Later this corridor was used for the First Transcontinental Railroad.

The highway was originally State Route 30. The highway first appeared on the official Nevada state highway map in 1933. The connecting highway in Utah was originally numbered State Route 70, but was renumbered Route 30 in 1966. With this change the highway carried the number 30 on both sides of the state line. The highway was re-numbered State Route 233 as part of a mass renumbering of Nevada state routes. The 1978 edition of the official Nevada Department of Transportation state highway map was the first to show both numbers, with the 1982 edition the first to use only the 233 designation.

The entire route is in Elko County.